Abstract

Digestibility, N balance and growth studies were carried out with local
goats to determine the effect of supplementing foliage of the legume tree
Bauhinia accuminata) with cassava foliage or water spinach (30-40% of
diet DM) with and without low levels of brewers’ grains (5% of diet DM).

The supplement of brewers’ grains improved the growth rate of the goats by
44% and the DM feed conversion by 25% when the protein supplement was
cassava foliage. Comparable data when water spinach was the protein
supplement were 11 and 5%. It is suggested that brewers’ grains, a fermented
byproduct from brewing “beer”, act as a prebiotic when added to a diet
containing potentially toxic elements such as the cyanogenic glucosides
present in cassava foliage.

Key words: biochar, prebiotics, protein solubility, synergism

Introduction

Research by Silivong and Preston (2015) showed that the growth rate of goats
fed foliage of the legume tree Bauhinia accuminata was increased by
supplementation with fresh water spinach and biochar. The protein in water
spinach is very soluble (Silivong and Preston 2015) and it is thought that
its role in improving the utilization of foliages of low digestibility, such
as Bauhinia accuminata, is because the water spinach acts as a
source of readily available nitrogenous compounds for rumen micro-organisms
(Silivong and Preston 2015, 2016).

The positive role of biochar as a supplement in ruminant diets is thought to
reflect another feature of ruminant nutrition, namely as a support mechanism
for biofilms that host consortia of micro-organisms facilitating the
utilization of nutrients with major benefits for the process of rumen
fermentation (Leng 2014). In this role, it appears that biochar is acting as
a “prebiotic”, by promoting synergism between nutrients and micro-organisms
in the animal’s digestive system.

A similar synergism appears to be the explanation for the beneficial effects
on growth rates of cattle (Binh et al 2017) and goats (Sina et al 2017) of
small proportions in the diet of brewers’ grains, a byproduct derived from
the industrial brewing of beer. The research with goats (Sina et al 2017)
highlighted a major interaction between the effect of the supplementary
brewers’ grains and the nature of the basal diet. The improvement in growth
rate due to addition of brewers’ grains was 130% when the basal diet was
fresh cassava foliage but only 30% when the basal diet was water spinach
(Sina et al 2017).

The hypothesis that was tested in the present experiment was that goats fed
foliage of the legume tree Bauhinia accuminata wwould respond
positively in growth rate and feed conversion to a supplement of brewers’
grains, and that the degree of response would be greater when cassava
foliage, rather than water spinach, was the complementary source of protein.

Materials and Methods

Location and duration

The experiments were conducted in the Department of Animal Science Farm,
Souphanouvong University, Luang Prang Province, Lao PDR, from August 2017 to
January 2018.

In thedigestibility study (Table 1) the design was a 4*4 Latin
Squarewith 4 female goats and 4 periods each of 12 days: 7 days
for adaptation and 5 days for collection of feed refusals, feces and urine.

Table 1.
Layout of the digestibility/N retention study

Period

Goat 1

Goat 2

Goat 3

Goat 4

1

BWBG

BW

BCFBG

BCF

2

BCF

BWBG

BW

BCFBG

3

BCFBG

BCF

BWBG

BW

4

BW

BCFBG

BCF

BWBG

The goats (local breed) weighed 15.5±0.65 kg and were 5-6 months of age.
They were purchased from farmers around Luang Prabang city. They were housed
individually in metabolism cages made from bamboo (dimensions of width 0.8
m, length 0.9 m and height 1 m), designed to collect separately feces and
urine.

In the growth study the design was a random block with 4 replications of the
two factors in a 2*2 factorial design, with sixteen goats (balanced males
and females) with initial body weight of 14.4 ± 1.45 kg and 5-6 months of
age. They were housed in individual pens made from wood and bamboo.

In both studies, the goats were vaccinated against Pasteurellosis and Foot
and Mouth disease and were de-wormed before the start of the experiment.

Feeding and management

Foliages of Bauhinia accuminata and water spinach (Ipomoea
aquatica) were collected daily from natural stands in and around the
University campus. Cassava (Manihot esculenta Crantz) foliage was
collected daily from a demonstration plot in the Department of Animal
Science Farm. Cassava root was harvested from the demonstration plot in the
department of Animal Science Farm. It was chopped into small pieces and
exposed to sunlight for 48h to reduce the moisture to about 15%. Brewers’
grains were purchased from a brewery in Vientiane city.

The biochar was produced by burning rice husks in a top lit updraft (TLUD)
gasifier stove (Olivier 2010). It was ground to a particle size that passes
through a 1 mm sieve. The biochar was mixed with the cassava root chips and
fed from a plastic bucket. Bauhinia foliage, water spinach and cassava
foliage were hung in bunches above the feed trough (Photos 1-3). Fresh feeds
were offered twice daily at 07:30 and 16:00h. Water was freely available.

Photo 1. Cassava foliage hanging above the feed trough

Photo 2. Water spinach hanging above the feed trough

Photo 3. Bauhinia accuminata hanging above the feed trough

Measurements

Metabolism study

Live weight was recorded in the morning before feeding at the beginning and
at the end of each period. Feeds offered, and refusals were collected daily
during the 5 days of the collection period. Urine was collected in buckets
with 20 ml of a solution of sulphuric acid to ensure a pH of less than 4
(10% sulphuric acid concentrate + 90% distilled water). Feces and urine were
collected daily and stored in the refrigerator (4-8ºC) until the end of each
period, when sub-samples were mixed together.

Growth study

Live weight was recorded in the morning before feeding at the beginning and
at 10-day intervals until the end of the 90-day experiment. Live weight gain
was calculated from the linear regression of live weight (Y) on days from
the start of the experiment (X).

FeFeed consumption was recorded daily. Refusals were collected from individual
animals every morning before offering new feed. Samples of Bauhinia, water
spinach and cassava foliage (offered and residues) were separated into stems
and leaves (containing attached petioles). Representative samples of each
component were stored at -18°C until they were analysed. Samples of rumen
fluid were taken on the last day of the experiment, using a stomach tube.

Statistical analyses

Metabolism study

The data were analyzed by the general linear model (GLM) in the ANOVA
program of the Minitab software (Minitab 2000).

The statistical model used in the digestibility study was:

Yijk = μ + Ti + Pj +Ak + e
ijk

Where, Yijk = Dependent variables

μ = Overall mean

Ti = treatment effect (i=1-4)

Pj = column effect (j=1-4)

Ak = row effect (k=1-4)

eijk = random error

Growth study

The statistical model was:

Yijk = μ + Bk + Pi + Aj + P
i*Aj+ eijk

μ = Overall mean

Bk= Block effect

Pi = replacing water spinach by cassava foliage

Aj = with or without Brewers’ grains

Pi*Aj = Interaction between source of protein (water
spinach or cassava foliage) and with or without brewers’grains

eijk = random error

Results and discussion

Chemical composition of diet components

The low values for solubility of the protein in the leaves of Bauhinia and
cassava, and the high values for the leaves of water spinach (Table 2), are
in agreement with previous observations (Silivong and Preston 2016) and are
assumed to reflect different levels of tannin-rich compounds in the leaves
of all three species.

Metabolism study

The two factors had contrasting effects on digestibility of DM and on daily
N retention (Table 3). Supplementation with brewers’ grains increased the
digestibility of DM but the effect was more pronounced when cassava foliage
was the source of additional protein as compared with water spinach. Daily N
retention was similar for both foliages in the absence of brewers’ grains
but, when brewers’ grains were added, N retention was greater with cassava
than with water spinach (Figure 1).

Table 3.
Mean values of apparent digestibility and N balance in
goats fed Bauhinia accuminata supplemented with
water spinach or cassava foliage, with (BG) and without
(No-BG) brewers’ grains

Figure 2. Effect of brewer’s grain on N retention as % of digested N in goats fed Bauhinia accuminata and water spinach or cassava foliage as supplementary protein source

Growth study

The Bauhinia foliage accounted for two thirds of the total DM consumed
(Table 4; Figure 3). Other components were in similar proportions in each of
the diets, except for the brewers’ grains which was slightly higher (5% of
diet DM) compared with the planned level of 4% of diet DM. Addition of the
brewers’ grains resulted in a small increase in diet crude protein content
from 13.6 to 14.2% and from 13.8 to 14.5%, for the cassava foliage and water
spinach treatments, respectively.

There was an interaction between the effects of the two dietary factors on
DM intake, growth rate and DM feed conversion (Table 5). When the
protein-rich foliage was from cassava, the supplement of brewers’ grains
increased the DM intake and the growth rate and improved the feed conversion
but did not affect these criteria when the supplementary protein source was
water spinach (Figures 3 and 4). This result is in line with the findings of
Sina et al (2017) who supplemented brewers’ grains (5% of diet DM) to goats
fed fresh cassava foliage or water spinach, as the sole diet. In that study
there was a 129% increase in live weight gain when brewers’ grains were
added to cassava foliage, compared with only 25% improvement on the water
spinach diet.

Table 5.
Mean values for live weight, live weight change, DM intake
and DM feed conversion for goats fed Bauhinia
accuminata supplemented with cassava or water spinach
foliage, with or without brewers’ grains (interaction
effects)

Figure 4. Effect of a supplement of brewers’ grains on live weight gain of goats fed Bauhinia accuminata in combination with cassava foliage (CF) or water spinach (WS).

Figure 5. Effect of a supplement of brewers’ grains on DM feed conversion of goats fed Bauhinia accuminata in combination with cassava foliage or water spinach.

The higher values for rumen ammonia on the diets with water spinach (Table
6) were to be expected in view of the greater solubility of the protein in
water spinach compared with cassava foliage (Table 1). However, on all
diets, ammonia levels were sufficiently high to support normal rumen
function. On each foliage source, rumen ammonia values were higher when
brewers’ grains were included in the diet.

There were minor differences in molar proportions of the VFA, and the Ac:Pr
ratio, apparently related to the treatments; however, the small order of
magnitude of the differences means they are unlikely to be of importance in
relation to animal performance.

Table 6.
Molar VFAproportions in rumen fluid
from goats fed Bauhinia accuminata
supplemented with water spinach or cassava foliage, with
and without brewers’ grains

Cassava foliage

Water spinach

SEM

p

No-BG

BG

No-BG

BG

Acetic

65.6

64.9

66.3

64.8

0.28

0.174

Propionic

24.8 a

23.5 b

24.1 ab

24.6 a

0.29

0.008

Butyric

9.63

11.6

9.65

10.8

0.07

<0.001

Ac:Pr

2.64

2.76

2.75

2.64

0.04

0.017

pH

7.06

7.05

6.99

6.90

0.03

0.233

NH3, mg/liter

186d

194c

215b

232a

1.85

0.003

abcd
Mean values without common superscript differ at
p<0.05

Discussion

We propose that the interaction in the degree of improved animal
performance, according to whether the brewers’ grains were added to the diet
with cassava foliage, compared with the diet containing water spinach, was
because the brewers’ grains act as a prebiotic when included in diets
containing potentially toxic elements such as the cyanogenic glucosides
present in cassava foliage. A similar explanation can be applied to the
effects of “Kilao” (the byproduct from the fermentation/distillation of
“rice wine”) in increasing growth and feed conversion of cattle fed ensiled
cassava root and cassava foliage (Sengsouly and Preston 2016).

The improved performance appears to be manifested by increased diet
digestibility and improved biological value of the digested protein. The
greater response to brewers’ grains when cassava foliage was fed, compared
with water spinach, could be because of enhanced capacity to detoxify the
cyanogenic glucosides present in cassava foliage as reported by Binh et al
(2017).

Conclusions

Supplementing growing goats with brewers’ grains (5% of diet DM) increased
diet digestibility and the biological value of the absorbed protein,
resulting in improvement of live weight gain of 44% and in DM feed
conversion of 25% when the basal diet was a legume tree foliage (Bauhinia accuminata) and the protein supplement was cassava foliage.
Comparable data when water spinach was the protein supplement were relative
improvements of 11 and 5%.

It is proposed that brewers’ grains, a fermented byproduct from brewing
“beer”, act as a prebiotic when added to a diet containing potentially toxic
elements such as the cyanogenic glucosides present in cassava foliage.

Silivong P and Preston T R 2015
Growth performance of goats was improved when a basal diet of foliage of
Bauhinia accuminata was supplemented with water spinach and biochar.
Livestock Research for Rural Development. Volume 27, Article #58.
Retrieved March 20, 2015, from
http://www.lrrd.org/lrrd27/3/sili27058.html

Whitelaw F G, Preston T R and Dawson G S 1961
The nutrition of the early weaned calf, 2: A comparison of commercial
groundnut meal, heat-treated groundnut meal and fish meal as the major
protein source in the diet, Animal Production 3:127.

Received 9 February 2018; Accepted 22 February 2018; Published 1 March 2018